From: janosch84@...
Date: 2019-06-15T11:10:56+00:00
Subject: [ruby-core:93158] [Ruby trunk Misc#15925] Speed up SortedSet#min,	#max, #sum etc.?

Issue #15925 has been reported by janosch-x (Janosch M�ller).

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Misc #15925: Speed up SortedSet#min, #max, #sum etc.?
https://bugs.ruby-lang.org/issues/15925

* Author: janosch-x (Janosch M�ller)
* Status: Open
* Priority: Normal
* Assignee: 
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this issue is somewhat similar to https://bugs.ruby-lang.org/issues/15807

current situation, using the example of `SortedSet#min` (without `rbtree`):

- `SortedSet#min` calls `Enumerable#min`
- `Enumerable#min` calls `SortedSet#each`
- `SortedSet#each` calls `SortedSet#to_a`
- `#to_a` returns an `Array` which is guaranteed to be sorted
- `Enumerable#min` wastefully goes through this whole `Array` anyway

so complexity can be reduced from O(n) to O(1) for `#min`/`#max`/`#minmax`.

other methods may be sped up by delegating to faster implementations on `Array`.

for instance, `SortedSet.new(1..1000).to_a.sum` is an order of magnitude faster than `SortedSet.new(1..1000).sum`.

suggestion:

```
class SortedSet < Set
  # [ ... ]
  # non-rbtree case
  # [ ... ]

  def min
    to_a.first
  end

  def max
    to_a.last
  end

  def minmax
    [min, max]
  end

  def sum
    to_a.sum
  end

  # maybe more?
end
```



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